Simple model of vertical dispersion of O3 in Bangkok, Thailand using regression method

Abstract

Bangkok, the capital city of Thailand, has experienced a degradation in air quality. In particular, ozone (O₃) concentrations frequently exceed Thailand’s National Ambient Air Quality standards. Various policies have been developed to manage air quality at near-surface levels; however, the assessment of air quality above these levels has been neglected. Analysis of O₃ concentrations and its precursors measured at various altitudes revealed that the vertical structures of the pollutants in Bangkok were stratified. While NO_x concentrations decreased with height, O₃ concentrations increased. These results emphasize the importance of air quality management above ground level, particularly in megacities with high-rise buildings, such as Bangkok. Assuming that the O₃ formation regime over Bangkok is VOC-limited, a simple model was developed based on a linear regression method to estimate the changes in O₃ concentrations with height. We found that the simple model was able to capture the variation in O₃ concentrations at 30, 75, and 110 m above ground level, with an R² of 0.48–0.65. Although the simple model had some difficulty estimating the magnitude of O₃ concentrations, the estimated O₃ values from the model were reasonable for capturing vertical O₃ trends. Using this approach, policymakers can visualize the vertical distribution of pollutants, which will be useful in designing air quality management plans.